Php - Count consecutive values in array

user8918437
July 11, 2023
268 views
3 votes
5 Answers

I am fetching data from a mysql database that looks like this:

ID	Status
1	Green
2	Red
3	Red
4	Green
5	Green
6	Green
7	Green
8	Grey

And I want to find out, what is the highest consecutive count of Red, Green and Grey.

The outcome should be

Green: 4

Red: 2

Grey: 1

I tried How to count the consecutive duplicate values in an array? and Count Number of Consecutive Occurrence of values in Table but this is not exactly what I need.

I dont want to count every occurance and sum it up. I want to know the highest consecutive count of all of them.

I have tried the following, but it only works for certain scenarios.

$consecResult = array();
$prev_value = array("value" => null, "amount" => null);
while($row = $result->fetch_assoc())
{
    if ($prev_value['value'] != $row['status']) 
    {
       unset($prev_value);
       $prev_value = array('value' => $row['status'], 'amount' => 0);
       $consecResult[$row['status']] =& $prev_value;
    }

    $prev_value['amount']++;
}

Hope that makes sense!

Thanks!

Tags: arrays php

Answers

Chosen as BEST ANSWER

The answer is already in my question. The provided code does work if I loop through a nice array. I hope I did not make the array fit the solution ;-)

Anyway. This is how you can reproduce it!

<?php

$status[0]['status'] = "Green";
$status[1]['status'] = "Red";
$status[2]['status'] = "Red";
$status[3]['status'] = "Green";
$status[4]['status'] = "Green";
$status[5]['status'] = "Green";
$status[6]['status'] = "Green";
$status[7]['status'] = "Grey";

$consecResult = array();
$prev_value = array("value" => null, "amount" => null);
foreach($status as $stat)
{
    if ($prev_value['value'] != $stat['status']) 
    {
        unset($prev_value);
        $prev_value = array('value' => $stat['status'], 'amount' => 0);
        $consecResult[$stat['status']] =& $prev_value;
    }

    $prev_value['amount']++;
}

echo "<pre>";
print_r($consecResult);

?>

RESULT

Array
(
    [Green] => Array
        (
            [value] => Green
            [amount] => 4
        )

    [Red] => Array
        (
            [value] => Red
            [amount] => 2
        )

    [Grey] => Array
        (
            [value] => Grey
            [amount] => 1
        )
)

UPDATE TO RESULT

Turns out Answer #1 is not correct and the array was indeed made to fit the solution.

If you test with

$status[0]['status'] = "Green";
$status[1]['status'] = "Green";
$status[2]['status'] = "Green";
$status[3]['status'] = "Green";
$status[4]['status'] = "Red";
$status[5]['status'] = "Red";
$status[6]['status'] = "Grey";
$status[7]['status'] = "Red";
$status[8]['status'] = "Grey";
$status[9]['status'] = "Green";

the result will be

Array
(
    [Green] => Array
        (
            [value] => Green
            [amount] => 1
        )

    [Red] => Array
        (
            [value] => Red
            [amount] => 1
        )

    [Grey] => Array
        (
            [value] => Grey
            [amount] => 1
        )
)

Question is, what is missing? :-)

(Edit)

- TomasRuzicka
- July 11, 2023 at 12:41 pm
- 0 votes
0
Since you are using mysql, it might be good idea to leave the dirty work to database and use GROUP BY function on status column and then retrieve the result array.
```
SELECT COUNT(ID), Status
FROM color_table
GROUP BY Status
ORDER BY COUNT(ID) DESC; 
```
You can find example for this on this page

PHP & MYSQL: using group by for categories
Login or Signup to reply.

Here’s the algo for your use case. Should work on any other use case:

<?php
$status[0]['status'] = "Green";
$status[1]['status'] = "Green";
$status[2]['status'] = "Green";
$status[3]['status'] = "Green";
$status[4]['status'] = "Red";
$status[5]['status'] = "Red";
$status[6]['status'] = "Grey";
$status[7]['status'] = "Red";
$status[8]['status'] = "Grey";
$status[9]['status'] = "Green";

$curr_count = 0;
$consecResult = array();
$prev_value = null;

foreach($status as $stat) {

    $value = $stat['status'];
    
    # if value doesn't exist in consecResult, add the value with amount = 1 (if already exist, pass)
    if (! array_key_exists($value, $consecResult)) {
        $consecResult[$value] = array('value' => $value, 'amount' => 1);
    }
    
    # if prev_value is same as the value, increment the count variable else set it back to 1
    $curr_count = ($prev_value == $value) ? $curr_count + 1 : 1;
        
    # if amount of the value in consecResult array is lesser than current consecutive count ($curr_count), set new value. Otherwise, pass
    if ($consecResult[$value]['amount'] < $curr_count) {
        $consecResult[$value]['amount'] = $curr_count;
    }
    
    $prev_value = $value;

}

echo "<pre>";
print_r($consecResult);
?>

RESULT

Array
(
    [Green] => Array
        (
            [value] => Green
            [amount] => 4
        )

    [Red] => Array
        (
            [value] => Red
            [amount] => 2
        )

    [Grey] => Array
        (
            [value] => Grey
            [amount] => 1
        )

)

$input = [
  [ 'ID' => 1, 'Status' => 'Green' ],
  [ 'ID' => 2, 'Status' => 'Red' ],
  [ 'ID' => 3, 'Status' => 'Red' ],
  [ 'ID' => 4, 'Status' => 'Green' ],
  [ 'ID' => 5, 'Status' => 'Green' ],
  [ 'ID' => 6, 'Status' => 'Green' ],
  [ 'ID' => 7, 'Status' => 'Green' ],
  [ 'ID' => 8, 'Status' => 'Grey' ]
];

$result =
  array_map(
    'max',
    array_reduce(
      array_column($input, 'Status'),
      function ($carry, $status) {
        if ($carry[1] === $status) {
          $carry[0][$status][array_key_last($carry[0][$status])]++;
        } else {
          $carry[0][$status][] = 1;
          $carry[1] = $status;
        }
        return $carry;
      },
      [ [], '' ]
    )[0]
  );

print_r($result);

Output:

Array
(
    [Green] => 4
    [Red] => 2
    [Grey] => 1
)

Short explanation:

array_reduce starts with this initial result array:

[ 
  [],  // will hold all the counts for each color (not only the highest one)
  ''   // will hold the value of 'status' of the prior item in the array
]

And it starts also with this input array:

array_column($input, 'Status')

The result of it looks like this:

Array
(
    [0] => Array
        (
            [Green] => Array
                (
                    [0] => 1   // first occurence of 'Green'
                    [1] => 4   // second occurence of 'Green'
                               // etc.
                )

            [Red] => Array
                (
                    [0] => 2   // first occurence of 'Red'
                               // etc.
                )

            [Grey] => Array    // first occurence of 'Grey'
                               // etc.
                (
                    [0] => 1
                )

        )

    [1] => Grey   // this item is then dropped by using [0]
)

The last step is to apply max to each color item in the result array within array_map.

I have tested both arrays which you have shared i.e.

$status[0]['status'] = "Green";
$status[1]['status'] = "Red";
$status[2]['status'] = "Red";
$status[3]['status'] = "Green";
$status[4]['status'] = "Green";
$status[5]['status'] = "Green";
$status[6]['status'] = "Green";
$status[7]['status'] = "Grey";

AND

$status[0]['status'] = "Green";
$status[1]['status'] = "Green";
$status[2]['status'] = "Green";
$status[3]['status'] = "Green";
$status[4]['status'] = "Red";
$status[5]['status'] = "Red";
$status[6]['status'] = "Grey";
$status[7]['status'] = "Red";
$status[8]['status'] = "Grey";
$status[9]['status'] = "Green";

And my code works as expected.

Here is my code:

$status = array();
$status[0]['status'] = "Green";
$status[1]['status'] = "Green";
$status[2]['status'] = "Green";
$status[3]['status'] = "Green";
$status[4]['status'] = "Red";
$status[5]['status'] = "Red";
$status[6]['status'] = "Grey";
$status[7]['status'] = "Red";
$status[8]['status'] = "Grey";
$status[9]['status'] = "Green";

$highestCounts = array(
    'Green' => 0,
    'Red' => 0,
    'Grey' => 0
);

$currentCounts = array(
    'Green' => 0,
    'Red' => 0,
    'Grey' => 0
);

$previousStatus = '';

foreach ($status as $item) {
    $currentStatus = $item['status'];

    if ($currentStatus === $previousStatus) {
        $currentCounts[$currentStatus]++;
    } else {
        $currentCounts[$currentStatus] = 1;
    }

    $previousStatus = $currentStatus;

    // Update the highest count if necessary
    if ($currentCounts[$currentStatus] > $highestCounts[$currentStatus]) {
        $highestCounts[$currentStatus] = $currentCounts[$currentStatus];
    }
}

// Print the results
foreach ($highestCounts as $status => $count) {
    echo $status . ': ' . $count . "n";
}

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Php – Count consecutive values in array

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